Process for preparing coalesced spandex multifilaments

ABSTRACT

1. A PROCESS FOR PREPARING A COALESCED SPANDEX MULTIFILAMENT WHICH COMPRISES EXTTRUDING A SOLVENT SOLUTION OR MELT OF A SPANDEX POLYMER THROUGH A SPINNERET HAVING A PLURALITY OF ORIFICES TO FORM A PLURALITY OF SEPARATE FILAMENTS, PASSING THE SO FORMED FILAMENTS THROUGH A FIRST VORTICAL ZONE, THE FLUID OF WHICH CIRCULATES IN A GIVEN DIRECTION TO IMPART TO SAID PLURALITY OF SEPARATE FILAMENTS, BY APPLICATION THERETO OF A UNIDIRECTIONAL ROTATIONAL MOMENT, A FALSE TWIST WHICH EXTENDS BACK ALONG THE LINE OF THE FILAMENTS TO A POINT AT WHICH THE FILAMENTS ARE IN   A SUFFICIENTLY PLASTICIZED STATE TO ADHERE TO EACH OTHER, 0012A THEREBY FORMING A FALSE-TWISTED COALESCED MULTIFILAMENT, FOLLOWED BY PASSING SAID FALSE-TWISTED COALESCED MULTIFILAMENT THROUGH A SECOND VORTICAL ZONE, THE FLUID OF WHICH CIRCULATES IN A DIRECTION COUNTER TO THAT OF THE CIRCULATING FLUID OF THE FIRST VORTICAL ZONE, THEREBY REMOVING SAID FALSE TWIST BY APPLICATION OF A ROTATIONAL MOMENT IN A DIRECTION COUNTER TO THAT APPLIED IN THE FIRST VORTICAL ZONE, AND THEREAFTER TAKING UP SAID COALESCED MULTIFILAMENT.

Oct 1974 SHINJI YAMADA H L 5 PROCESS FOR PREPARING COALESCED SPANDEX HULTIFILAMEXTS 2 Sheds-Sheet 1 Filed 00%. 12. 1971 Y 2 2 1''.AQUBBH 171/ I w g El nnunu 1974 sum." YAMADA E L 4 PROCESS FOR PREPARING COALESCED SPANDEX HUL'I'IFILAMENTS Filed Oct. 12. 1971 2 Sheets-Shoot 'l United States Patent 3,840,630 PROCESS FOR PREPARING COALESCED SPANDEX MULTKFHLAMENT S Shinji Yamada and 'Isamu Takahashi, Iwakuni, Japan, assignors to Teijin Limited, Osaka, Japan Filed Oct. 12, 1971, Ser. No. 188,368 Claims priority, application Japan, Oct. 15, 1970, 45/913,061 Int. Cl. DOM 1/20 US. Cl. 264103 7 Claims ABSTRACT OF THE DISCLOSURE A process for preparing coalesced spandex multifilaments which comprises extruding a solvent solution or melt of a spandex polymer through a spinneret having a plurality of orifices to form a plurality of separate filaments, passing the so formed filaments through a first vortical zone, the fluid of which circulates in a given direction to impart to the plurality of separate filaments, by application thereto of a unidirectional rotational moment, a false twist which extends back along the line of the filaments to a point at which the filaments are in a sufliciently plasticized state to adhere to each other, thereby forming a false-twisted coalesced multifilament, followed by passing the false-twisted coalesced multifilament through a second vortical zone the fluid of which circulates in a direction counter to that of the circulating fluid of the first vortical zone, thereby removing the false twist by application of a rotational moment in a direction counter to that applied in the first vortical zone, and thereafter taking up said coalesced multifilaments.

This invention relates to a process for preparing spandex multifilaments in which the individual filaments are in coalescence with one another.

The spandex filaments obtained by dryor melt-spinning possess tackiness immediately after their extrusion. Therefore, it is well known that if a plurality of spandex filaments are brought together immediately after they have been extruded from a spinneret having a plurality of orifices, a coalesced multifilament bundle is obtained. The coalesced multifilament is superior to the single spandex filament yarn in the point that such a yarn is not easily broken in the subsequent processing steps. In US. Pat. 3,094,374 and Japanese Patent Application Publication No. 15,572/ 69 it is disclosed that in preparing a spandex multi filament the multifilament yarn consisting of a plurality of individual filaments spun from a spinneret is imparted a false twist by means of a vortex of circulating gas or liquid to cause the interfilament coalescence of the individual filaments making up the yarn, after which the yarn is taken up by a godet roll to thereby prepare a spandex multifilament which does not easily break during the subsequent processing steps.

However, when a false twist remains in the spandex multifilament (referred to herein as a coalesced filament at times) wherein the individual filaments making up the multifilament are in coalescence with one another as described above, the threadline on the godet roll is not stable and it frequently happens that the coalesced filament slips off the godet roll rendering it impossibe to continue the windup operation. Further, even though it may be possible to continue the winding operation, the presence of S and Z twists in the woundup filament causes various problems in the subsequent processing and treatment steps as a result of the twist or twist torque that remains in the coalesced filament. Therefore, in the process described it is necessary to remove the residual false twist substantially competely by the time the coalesced filament reaches the godet roll.

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3,840,630 Patented Oct. 8, 1974 "ice However, since the spandex multifilament, as compared with the other textile fibers, has an exceedingly great elasticity and an extremely small rigidity, various difficulties are experienced in removing the false twist remaining in the coalesced filament in a substantially complete manner. For example, as taught in US. Pat. 3,094,374 to remove the residual false twist by the time the coalesced filament reaches the godet roll by providing a tension sufiicient to remove the false twist, the spinning draft and the spinning speed must be increased tremendously. However, when the spinning is carried out under such conditions, this not only makes for instability of the spinning conditions but also results in a decline in the elongation and uniformity of the filaments. Moreover, even though the spinning is carried out under theseconditions, the threadline on the godet roll is still not stabilized, and therefore the stable winding of the yarn is not easily accomplished.

It is an object of this invention to provide a method for forming a coalesced spandex multifilament having high elasticity and superior interfilament adhesion. Another object is to achieve virtually complete and continuous coalescence of dryor melt-spun spandex filaments. A further special object is to provide a process which can prepare a coalesced spandex multifilament which excels in elongation and uniformity as well as in which substantially no twist remains by removing without application of any tension the false twist which has been imparted to the coalesced multifilament. Other objects will appear hereinafter.

These and other objects are accomplished by a process which comprises extruding a solvent solution or a melt of a spandex polymer through a spinneret having a plurality of orifices to form a plurality of separate filaments. Next, the so formed filaments are passed through a first vortical zone in which the flow of the vortex is in a given direction to impart to the plurality of separate filaments, by application thereto of a rotational moment in one direction, a false twist which extends back along the line of the filaments to a point at which the filaments are in a sufficiently plasticized state to adhere to each other, thereby forming a false-twisted, coalesced multifilament. This is followed by passing this false-twisted, coalesced multifilament through a second vortical zone in which the flow of the vortex is in a direction counter to that of the vortex of the first vortical zone, thereby removing the false twist by application of a rotational moment in adirection counter to that applied in the first vortical zone, and thereafter taking up the coalesced multifilament.

The spandex multifilament is usually produced in the following manner: (a) a dryor wet-spinning method which comprises spinning a polyurethane polymer solution from a spinneret into a dry medium or a coagulating bath to solidify the filaments, (b) a melt-spinning method which comprises heat-melting the polyurethane polymer and spinning the melt from a spinneret into a cooling medium to cool and solidify the filaments, or (c) a reaction spinning method which comprises carrying out the concurrent spinning and reaction of the several reaction components which are capable of forming the I polyurethane polymer.

Of the foregoing methods, the process of the present invention is applicable where the yarn is prepared by either the dryor melt-spinning technique.

The invention process will be more fully described with reference to the accompanying drawings, wherein:

FIGS. 1 and 2 are each drawings for illustrating the modes of practicing the invention, each being a sectional view of apparatus for preparing a spandex multifilament; FIGS. 3, 4 and 5 are each drawings illustrating the designs of jet twisters suitable for use in the invention, the

(a) figure in each case being a plan view, while the (b) figure is a sectional view taken along the line AA of the (a) figure.

Referring to FIG. 1 which illustrates an instance in which the spinning is by the dry technique, the polyurethane polymer solution is spun from a spinneret 1 into filaments, which, while traveling through a spinning cell 2 to which a dry hot gas stream is introduced from the top, have solvent removed by evaporation to thereby solidify and form multifilaments Y. At this time a vortex of gas circulating is a given direction is exerted on the multifilament at a first jet twister 5 disposed below the spinning cell to impart a false twist to the multifilaments. The topmost part T of this false twist extends back into the spinning cell 2. Therefore, the individual filaments of the multifilament in a plasticized state inside the spinning cell become coalesced with one another as a result of this false twist. The coalesced filaments Y, the individual filaments of which have been coalesced by having been imparted a false twist by the first jet twister 5, proceed to a second jet twister 6 while still retaining the imparted false twist. At this second jet twister, a vortex of gas circulating in a direction counter to that of the first jet twister is exerted on the false-twisted filaments, with the consequence that the filaments are applied a rotational moment counter to the false twist remaining in the coalesced filaments, thereby removing the false twist essentially completely. Thus, the coalesced filaments arrives at the first godet roll 7 in a state substantially free of twist and are wound up by means of the winding apparatus (not shown) via an oiling roll 8 and a second godet roll 9.

In FIG. 2, which illustrates an instance where the spinning is carried out by the melt technique, the polyurethane polymer melt spun from a spinneret 1' is cooled and solidified in a spinning cell 2' by means of cool air blown to the freshly spun filaments through a plurality of perforations, thereby forming filaments Y. Then the filaments pass through a first jet twister 5' which uses water for imparting a false twist to the filaments by a torque thereof, with the consequence that the individual filaments are adhered to one another. Next, the false-twisted filaments proceed to a second jet twister 6' which uses air. At this jet twister an untwisting operation is carried out by means of a vortex of air circulating in a counter direction. As a result, coalesced filaments substantially free of twist are wound up as in the same operation as in FIG. 1.

As the vortex for use in imparting a false twist to the filament in this invention and in untwisting the false twist remaining in the filaments, conveniently available are the vortex of liquid, gas or a mixture of liquid and gas. While air is most advantageous from the commercial stand point, steam, combustion gas as well as other inert gases are also available. On the other hand, water is a commercially advantageous liquid, but other inert liquids can also be used. When using these fluids, the vortices circulating in directions counter to each other may be both fluids of the same class as in the case of FIG. 1, or one may be a gas and the other may be a liquid as in the case of FIG. 2. Further, if a finishing agent is dispersed or dissolved in the gas or liquid which is used, the subsequent finishing operation can be omitted.

The jet twister by which the circulating fluid exerts a torque on the filaments can be of any design as long as it is one which can impart an effective rotational moment by means of a circulating stream. While the jet twister mentioned in US. Pat. 3,094,374 can be used, particularly suitable is one which not only imparts a torque on the filaments but also has a propellant action.

FIGS. 35 illustrate such jet twisters which are conveniently used in the invention. In these figures, 10 is the central hole through which the filaments pass, 11 is the feed inlet for the fluid and 12 is the orifice for introducing the fluid into the central hole. As shown in FIG. 3, the jet twister is of such a design that the filament inlet side of the central hole is made small, while the outlet side is made large; or as in FIGS. 4 and 5, the disposition of the fluid orifices is so designed that the fluid is jetted obliquely downwardly, thereby ensuring that the whole or a major part of the vortex proceeds downwardly as it circulates in the central hole 10. In the case of the jet twister shown in FIG. 3, the ratio of the diameter of the filament inlet of the central hole to the diameter of the filament outlet is preferably 1:1.5-1 10, a ratio of 1:21:3 being still more preferable. The size of the inlet and outlet will depend on the denier of the coalesced filament. Usually one is used in which the diameter of the inlet ranges between w/denier In some cases, a twister which is a modification of the type shown in FIG. 3, such as a type having a pipe of an inside diameter somewhat larger than that of the central hole 10 joined at the outlet end of the twister and extending straightly and downwardly therefrom is conveniently used. By a provision such as this, the excessive ballooning of the filament, which has emerged from the twister, can be prevented. In the twister of the type shown in FIG. 4, that in which the fluid orifice 12 is inclined at an angle of 15 degrees to 75 degrees relative to the filament passage is suitably used. When the foregoing angle exceeds 75 degrees, i.e. approaches perpendicularity, the action by which the filament is propelled downwardly is weakened. On the other hand, when this angle becomes less than 15 degrees, the stability of ballooning of the filament is aggravated and the filament of uniform denier and tension can not be obtained. When jet twisters of the types described are used, the filament is imparted a propellant action inside the twister, and therefore not only is the stringing up of the jet twister facilitated but also the tension of the filament inside the twister and downwardly therefore can be reduced to a very small value.

Further, a total of three or more jet twisters can be used for carrying out the false twisting and untwisting operations in the invention process. For example, the false twist may be imparted gradually by passing the filaments successively through two jet twisters each having vortical fluid circulating in the same direction, following which the filament is untwisted by passing through one or more jet twisters having a vortical fluid circulating in a counter direction.

In either case, the intensities of the vortex used for carrying out the false twisting and that used for carrying out the untwisting must be suitably chosen in accordance with the denier of the filaments, the spinning speed, the design of the jet twisters and kind of the fluid used. However, when the fiuid used is the same, a rate of flow ratio based on the amount of flow of the two vortices in a range of 2: 1-1 :2 is to be preferred.

For example, when the following type of jet twister is used, the preferable rates of the fluid flows are as shown in Table A.

Type of jet twistershown in FIG. 3

Diameter of central hole (10)-812 mm. Minimum diameter of filament inlet3-5 mm. Sectional area of fluid orifice--12 mm. x 5-10 mm.

denier (mm.) and TABLE A Fluid Air Water Jet twister for false twisting (L/min.) 10-50 2=l5 Jet twister tor untwisting (l./min.) 5-40 2-10 moments imparted to the filaments by the respective vortices would offset each other, with the consequence that no substantial false twist could be imparted to the filaments. However, surprisingly, in the case of a spandex multifilament, there is practically no interaction among rotational torques that are imparted by the vortices to the filaments in counter directions, and these torques have an effective action independently of each other. Therefore the false twisting and untwisting are smoothly accomplished by the respective vortices to thereby provide a coalesced filament substantially free of twist.

When the position at which the first vortex is to act on the filaments and the position at which the second vortex is to act on the filaments are disposed extremely close to each other, e.g., at an interval of 0.5 cm., an undesirable interference of the actions of the two vortices occurs and satisfactory false twisting and untwisting cannot be achieved, with the consequence that the degree of roundness and the evenness of the filaments sufl'er. Therefore, it is necessary to choose a suitable interval between the positions at which the two vortices are to act on the filaments. While this interval will vary depending upon the denier of the filaments, the spinning speed, the design of the jet twister and the kind of the fluid used, in general, an interval of at least about 1 cm. will do, but preferred is one of at least 5 cm., still more preferably above cm., and particularly preferred is one above cm., which should be suflicient in all cases.

The spandex polymers, i.e. segmented polyurethanes, from which the invention spandex multifilament is prepared, are generally prepared from hydroxyl-terminated prepolymers, such as hydroxyl-terminated polyethers and polyesters of low molecular weight. Reaction of the prepolymer with a molar excess of organic diisocyanate, preferably an aromatic diisocyanate, produces an isocyanate-terminated material which may then be chainextended with a difunctional, active-hydrogen containing compound, such as water, hydrazine, organic diamines, glycols, aminoalcohols, aminohydrazide, etc. Many segmented polyurethanes of this type are described in several patents and are useful in the practice of this invention. Among these are US. Pats. 2,929,800, 2,929,801, 2,929,802, 2,929,804, 2,957,852, 2,962,470, 2,965,437, and 3,467,626. As taught by the aforementioned patents, many of the segmented polyurethanes when in filament form display elongations at break in excess of 200%, elastic recovery (or tensile recovery) of above about 90%, and stress decay of below about 20%.

When it is desired to spin the filaments by the dryspinning technique, the segmented polyurethanes are preferably prepared by carrying out the polymerization reaction in the solvent to be used for spinning. Conventional procedures may be used for preparing such polymer solutions. Solvents which have been found satisfactory for use in the dry spinning operation include N,N-dimethylformamide, N,N dimethylacetamide, tetramethylenesulfone, formic acid, and mixtures of 1,1,2-trichloroethane with formic acid.

According to the invention process, which has been described above, as a result of the positive untwisting of a false twist imparted by a vortex by means of a vortex circulating in a direction counter to that of the first vortex, the tension during the travel of the filaments and during their take-up can be reduced to a very small value as compared with the method of removing the false twist by applying a. tension to the false-twisted filaments. As a consequence, the following functions or effects are demonstrated:

(1) Filaments of great elongation can be obtained.

(2) Even though fluctuation in tension occurs during the take-up of the filaments, the fluctuation in tension is absorbed along the way and the effect of such a fluctuation in tension does not extend back to the solidifying point of the filaments inside spinning cell. Therefore, the uniformity of the product is enhanced.

(3) Even though the filament contacts the inside wall of the jet twister during its travel, there is no possibility of the appearance of flufls or flattening of the filament section.

(4) Since it is possible to impart a sufficient rotational moment to the filaments even in the case where the vortex has a relatively low rate of flow, a satisfactory coalesced filament can be obtained. In addition, the fluid fed to the jet twisters need not be raised to a very high speed.

(5) The range of spinning conditions that can be employed is broadened. For example, spinning at low speed and low draft becomes possible.

Further, since the threadline on the godet roll is stable, the windup can also be carried out smoothly.

Moreover, a satisfactory product substantially free of twist and free of residual torque can be obtained by the mere suitably adjustment of the speeds of the fluid that is fed to each of the jet twisters.

The fiber obtained in accordance with the invention process is suitably used for lingerie, girdles, corsets, wig bases, and woven and nonwoven fabrics.

The following examples and control experiments are given for further illustration of the invention. In the examples, all percentages are percent by weight, and the measurement values are obtained in the following manner.

(a) Coefficiency of variance of denier The coefiiciency of variance of denier is calculated by the following equation:

Coefficiency of variance of denier(%) wherein 55 is an average value of weight of 18 cm. length filaments; and a is the standard deviation. Thirty samples are measured and the sampling is carried out in the following manner: First, 10 samples are taken successively along the length of the filament. Then 20 samples are taken along the length of the filament at S-meter intervals.

(b) Number of residual twists The number of residual twists is determined in the following manner. A filament 10 cm, in length is observed when relaxed in a loop state to determine whether the filament twists as a result of the false twist remaining in it. This determination is made times in succession on filaments each 10 cm. in length. The number of case in which a twist is present is designated the number of residual twists.

(c) Tenacity and elongation The tenacity and elongation of the filament are measured with an Instron tensile tester under standard conditions (temperature of 20 C. and a relative humidity of 65% at a pulling speed of 1000% per minute.

(d) Degree of roundness (circularity) The degree of roundness is an indication of the flatness of the coalesced filament and is shown by the ratio of the minimum diameter of the cross section of the coalesced multifilament to the maximum diameter thereof. The larger this value, the more round the cross section of the filament (the maximum value is 1.00); while the smaller this value, the flatter the filament.

EXAMPLE 1 A spandex polymer was made in the following manner following the procedure described in US. Pat. 3,467,626.

An isocyanate-terminated prepolymer was obtained by reacting polytetramethylene glycol (molecular weight 2000) with 4,4-diphenylmethane diisocyanate at a mol ratio of 1:2. A solution of the so obtained prepolymer in dimethylformamide and a dimethylformamide solution of beta-aminopropionic acid hydrozide were mixed, and by effecting the chain extension in the solution a polyurethane polymer solution of 30% concentration was obtained.

3% of a stabilizer and 2% of a delustrant were added to the foregoing solution, based on the polymer, to obtain a spinning dope, which was spun from a spinneret preheated at 105 C. into a spinning cell heated at 180 C. Hot air of 180 C. was blown into the spinning cell from the upper part thereof and discharged from the lower part of the cell along with the evaporated solvent.

The freshly spun filaments were imparted a false twist by means of a vortex at a first jet twister disposed directly below the spinning cell, thus causing the coalescence of the individual filaments of the multifilament inside the spinning cell. The false-twisted filament, which then entered a second jet twister disposed below the first twister, was untwisted by a vortex circulating in a counter direction. The filament then was wound up on a friction winder at the rate of 400 meters per minute via a first godet roll, an oiling roll and a second godet roll. A coalesced filament (440 denier/ 42 filaments) substantially free of twist was obtained.

The conditions under which the experiments were carried out and the results obtained are shown in Table l-l.

TABLE 1-1 Experiment A B C First jet twister:

Design Fluid Air Air Air Rate of flow (l./min.) 40 30 40 Second jet twister:

esign Fluid Air Air Air Rate of flow (l./min.) 30 25 30 Interval between the two jet twisters (cm 40 60 0.5 Filament tension before the first godet roll Properties of filament:

Number of residual twists:

S-twist 2 1 1 Z-tW'iSt 2 0 Elongation (percent) 680 600 650 Tenacity (g./d.) i 1. 08 1. 09 1. Denier variance (percent) 2. 03 2. 47 6 01 Roundness 0. 86 0. 79 0 37 1 That of FIG. 3.

2 That described in U.S. Pat. 3,094,374.

3 That of FIG. 4.

4 That described in U.S. Pat. 3,094,374. (For counter twist use.) 5 Small.

' Medium-small.

Experiment C was a comparative experiment which was carried out to show the effects on properties of the filament when the interval bet-ween the jet twisters was close. The coalesced filament was prepared as in Experiment A, but with the interval between the first and second jet twister shortened to a distance of 0.5 cm. The actions of the vortices of the first and second jet twisters exert on the filament forces which are counterdirectional to each other brought an unfavorable interactive effect on the filament such as to aggravate the stability of ballooning of the filament to result in worsening the uniformity and the roundness of the filament.

Control 1 In preparing a coalesced filament under the conditions of Example l-(A), instead of untwisting the filament with the second jet twister, an attempt was made to remove the twist and take up the filament by applying a tension to the filament by the method taught in U.S. Pat. 3,094,- 374. However, the filament would slip off the roll and it could not be taken up, since the twist remaining was great. So a hook was disposed between the first jet twister and the first godet roll, and by applying tension by rubbing the filament against the hook, the twist was removed and the filament was taken up. In this case, the filament tension before the first godet roll becomes great, with the consequence that the properties of the resulting coalesced filament, as shown in Table 1-2, were inferior in its elongation as well as denier uniformity as compared with the p oduct Obtained in accordance with the invention process.

8 TABLE 14 Properties of coalesced filament Number of residual twists:

A spandex multifilament denier/8 filaments) was obtained using the same dope as in Example 1 and op erating under substantially the same conditions. In this experiment inquiries were made into the instance where the false twist was imparted stagewise using two jet twisters (a first of a first set of jet twisters and a second of the first set of jet twisters and also the instance where the untwisting was carried out stagewise using two jet twisters (a first of a second set of jet twisters and a second of the second set of jet twisters).

The conditions under which each instance was carried out and the results obtained are shown in Table 2-1. (The interval between the jet twisters, as indicated in the table, is the interval between the first of the second set of twister and the twister disposed immediately thereabove.)

TAB LE 21 Experiment C D E First of first set of jet twisters:

D s Fluid Air Rate of flow (l./mi 7 25 7 Second of first set of jet twisters:

csign Fluid Air Rate of flow (l./min.) 15 Interval between jet twisters (cm.) 40 30 40 First of second set of jet twisters:

Design Fluid Air Air Air Rate of flow (Llmi 20 23 10 Second of second set of jet twisters:

Design Fluid Rate of fiow (l./min.) 15 Filament tension before 1st godet roll Properties of filament:

Number of residual twists S-twist 5 14 18 Z-tWist 7 18 11 Elongation ercent) 535 530 560 Tenacity d.) 1. 35 1. 28 1. 21 Denier vairanee (percent) 2. 63 2. 17 2. O1 Roundness 0. 81 0. 92 0. 84

1 That of FIG. 5. 2 That of FIG. 3. 5 Water. 4 N 01; used. 6 That of FIG. 4. Hot air. 7 Small.

Control 2 The spinning of the filaments was carried out under the conditions given in Example 2, disposing a single jet twister below the spinning cell to carry out the false twisting operation, followed by removing the twist under tension with or without the use of a hook.

The conditions under which the experiment was carried out and the results obtained are shown in Table 2-2.

1 Identical to that of Example 2(D). h ientical to that of Example 103).

4 N o. 5 Great. Medium-small.

In the case of Experiment (b), above, the cross section of the coalesced filament was fiat. Further, in the case of both Experiments (a) and (b) the threadline was not stable on the first godet roll and the filament would frequently slip off the godet roll making it impossible to take up the filament. Therefore, the filament properties in the foregoing table are values of only those which could be taken up. Again, in the Experiment (b), a higher flow rate such as 25 liters per minute made it impossible to carry out the Experiment. So the rate of air flow of 10 liters per minute was used.

EXAMPLE 3 To a mixture of polytetramethylene glycol (molecular weight about 1600) and polyethylenepropylene adipate (molecular weight 1100) was added 4,4-diphenylmethane diisocyanate in an amount such that the isocyanate groups are contained at a ratio of 1.15 to the hydroxyl groups, and as a result of the reaction, a spinning dope of 180 C. and 1100 poises was obtained. In this case, 2% of titanium dioxide was added with the polytetramethylene glycol.

After this spinning dope was defoamed and filtered, it was extruded through a spinneret (spinneret temperature 200 C.) having 5 orifices each 0.5 mm. in diameter into a spinning cell 5 meters in length. Room temperature air was introduced into the spinning cell for cooling the freshly spun filaments. The solidified filaments emerging from the spinning cell were then imparted a false twist by means of a vortex at a first jet twister disposed directly below the spinning cell, thereby effecting the coalescence of the individual filaments of the yarn inside the spinning cell. This was followed by untwisting the coalesced filament by imparting a counterdirectional rotation thereto by means of a second jet twister disposed below the first twister. The untwisted filament was then taken up via a first godet roll and after application of a finishing agent at the oiling roll was wound up by means of a friction winder at the rate of 450 meters per minute via a second godet roll.

A coalesced filament (220 denier) substantially free of twist was thus obtained. The conditions under which this experiment was carried out and the results obtained are shown in Table 3-1, below.

TABLE 3-1 First jet twister Design That of FIG. 5. Fluid Water. Rate of flow (l./min.) 8.

Second jet twister Design That of FIG. 4. Fluid Hot air (100 C.). Rate of flow (L/min.) 35.

Interval between jet twisters (cm.) 30. Properties of filament Number of residual twists S-twist, 2, Z-twist 3. Elongation (percent) 700.

Tenacity (g./d.) 0.91.

Denier variance (percent) 3.3.

Roundness 0.89.

In this example, since the filament emerging from the spinning cell is immediately cooled by means of the first jet twister, the solidification of the filament is completely carried out. Then the moisture adhering to the filament is practically completely removed by the hot air of the second jet twister. Therefore, the denier variance has been improved.

Control 3 Example 3 was repeated except that as the first jet twister that of FIG. 3 was employed, and as the fluid, air was introduced at the rate of 25 liters per minute, and instead of the second jet twister a hook was used. The experiment was otherwise carried out as in Example 10 3. As a result, a coalesced filament of 231 denier and having the properties shown in Table 3-2, below, was obtained.

1. A process for preparing a coalesced spandex multifilament which comprises extruding a solvent solution or melt of a spandex polymer through a spinneret having a plurality of orifices to form a plurality of separate filaments, passing the so formed filaments through a first vortical zone, the fluid of which circulates in a given direction to impart to said plurality of separate filaments, by application thereto of a unidirectional rotational moment, a false twist which extends back along the line of the filaments to a point at which the filaments are in a sufliciently plasticized state to adhere to each other, thereby forming a false-twisted coalesced multifilament, followed by passing said false-twisted coalesced multifilament through a second vortical zone, the fluid of which circulates in a direction counter to that of the circulating fluid of the first vortical zone, thereby removing said false twist by application of a rotational moment in a direction counter to that applied in the first vortical zone, and thereafter taking up said coalesced multifilament.

2. The process of claim 1 wherein said vortices of circulating fluid are so adapted that they circulate in helical fashion so as to advance in the direction of the travel of the filament as they circulate to thereby exert a rotational moment on the filament as well as a propellant action thereon.

3. The process of claim 1 wherein said first and second vortical zones are so disposed that they are spaced at least one centimeter from each other.

4. The process of claim 1 wherein said vortex of circulating fluid is a gas.

5. The process of claim 1 wherein said vortex of circulating fluid is a liquid.

6. The process of claim 1 wherein the circulating fluid of the first vortical zone is water and the circulating fluid of the second vortical zone is air.

7. The process of claim 1 wherein the ratio of the rate of flow of the fluid of the first vortical zone to the rate of flow of the fluid of the second vortical zone is in the range of 2:11:2.

References Cited UNITED STATES PATENTS 3,124,628 3/1964 Hughey 264-210 F 3,279,164 10/1966 Breen et a1 57-157 3,457,338 7/ 1969 Lefevre 264-103 3,558,757 1/ 1971 Denyes et al 264-205 3,043,088 7/1962 Breen 264-103 3,094,374 6/ 1963 Smith 264-103 3,342,027 9/ 1967 Mehler 264--103 3,501,908 3/ 1970 Mattingly 57-157 TS 3,656,288 4/ 1972 Gilchrist 57-157 3,695,025 10/1972 Gibbon 57-157 F 3,726,073 4/1973 Stutz 57-157 TS 3,727,392 4/ 1973 Gibbon 57-157 F FOREIGN PATENTS 10,405 6/1966 Japan 264-210 657,638 2/ 1963 Canada 264-103 JAY H. WOO, Primary Examiner U.S. C1. X.R.

57-157 F, TS; 264-205 

1. A PROCESS FOR PREPARING A COALESCED SPANDEX MULTIFILAMENT WHICH COMPRISES EXTTRUDING A SOLVENT SOLUTION OR MELT OF A SPANDEX POLYMER THROUGH A SPINNERET HAVING A PLURALITY OF ORIFICES TO FORM A PLURALITY OF SEPARATE FILAMENTS, PASSING THE SO FORMED FILAMENTS THROUGH A FIRST VORTICAL ZONE, THE FLUID OF WHICH CIRCULATES IN A GIVEN DIRECTION TO IMPART TO SAID PLURALITY OF SEPARATE FILAMENTS, BY APPLICATION THERETO OF A UNIDIRECTIONAL ROTATIONAL MOMENT, A FALSE TWIST WHICH EXTENDS BACK ALONG THE LINE OF THE FILAMENTS TO A POINT AT WHICH THE FILAMENTS ARE IN 